Experience with cylinder reduction, light variations in astigmatism requirements

My starting diopters were L: -2.5 sph with -1.25 cyl axis 150 and R: -4 sph (glasses prescription managed to add in some cyl in the right eye; thankfully I haven’t worn those all that much).

I got all excited when I started and ordered a pair of Zenni’s based solely on distance measurements which came out to L: -3.0 and R: -3.5, which seems sufficient correction for certain circumstances but not others.

Has anyone else noticed that astigmatism is pupil-dependent? One interesting thing I noticed was that in daylight when my pupil is contracted my left eye has better acuity than my right and the effects of the astigmatism diminish dramatically. Once the brightness decreases, the focus problems associated with astigmatism seem to become more pronounced and it becomes rather difficult to focus with my left eye due to the lovely induced astigmatism.

I concluded that dropping the entire -1.25 cyl was probably too aggressive for non-daylight conditions, but it’s clear that I don’t seem to need any cyl in daylight. It was also insufficient for reading and computer work, unfortunately.

After fiddling with the lens test kit I decided to retreat a bit and try a modest reduction to L: -2.5 sph -0.75 cyl axis 150, R: -3.75 sph which seems to achieve very similar acuity in both eyes. I ordered contacts and the acuity is probably 99% the same as the original with a little bit of astigmatism blur at night with point light sources. I figure I’ll give this one 90 day supply of contacts worth and reevaluate. Hilariously the optometrist wanted to bump me up to 4.25 in the right eye at the last exam because I didn’t quite get 20/20 at a -4. Alas…

What have people’s strategy been regarding cylinder reduction? I see a few routes:

  1. Abandon this and pay attention to the instructions to try reducing SPH only. CYL annoys me, in particular because they just snuck that in the past two years whereas prior I was SPH only.
  2. Continue on this path. Probably next try reducing SPH – concerned about reducing CYL by 0.75 in the next round. I could potentially try increasing SPH when I do the next CYL reduction? Or I may need to switch to glasses due to torric lens availability:

Another note is that torric contacts are not available in -0.5 cylinder or below, so there’s no way to lower that without going to regular contacts. Could do something ridiculously crazy like contacts normalized with SPH only and then contact-relative differentials with like +1.5 sph and -0.5 CYL in the L eye. I may also switch to glasses more full time at least while I adjust through CYL reduction.

Sorry for the ramble…

Interesting observation about the relationship between pupil size and astigmatism. As I have astigmatism in both eyes, -1 and -2, I can test this for myself. I have the bare light bulb over my laptop reflecting in a French door about 8 metres away. With uncorrected eyes, I see three overlapping light bulbs with my -1 astigmatic eye, and up to 8 lights bulbs, barely touching with my much more myopic -2 astigmatic eye, just tested in early dawn light. I will look again when there is full daylight and see if I can reduce the number of light bulbs.:grinning:
It have still not yet decided how and when I will address this cylinder challenge. Vague memories from the distant past tell me I had an astigmatism correction for the weaker eye with my first pair of glasses, but not for the stronger eye. I know how I developed this diopter ratio, both in sphere and astigmatism - reading in bed, usually on my right side, for up to 2 hours each night, and longer if it was a real thriller, or intellectually very stimulating.

Nick - what circumstances? Are you measuring for SPH and CYL?

Low light situations = less information for your eyeballs/optical cortex = worse vision.

You have a problem with your left eye in that your CYL/SPH ratio upon reduction for diff would be HUGE. You are going to have to play with this.

That’s it!. …scientist experimenting on his own eyeballs

The guidelines are ‘average’ rules based on Jake’s experiences with lots of pupils, but everyone’s eyes are different. Trust your own measurements and observations. You are off to a great start.

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The above experiment was obviously not well thought out. Even with daylight streaming into the many windows of my converted barn, I do not have the full pupil narrowing I would have outside. No difference, still the same number of light bulbs. I will have to wait until there is a clear moon in the early dawn, which still remains visible many hours later, and count the numbers of moons in the different light conditions. The last time I tried in good light, I saw 5 moons with the left, and only two with the right. Perhaps the fact that the French doors I tried with this morning are double glazed nearly doubled the number of light bulbs. :crazy_face:
Thank goodness I can do this all in a light-hearted manner, unlike the metabolic syndrome issues which were life-threatening.

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I was just measuring distance without using the astigmatism measuring setup to see if I could get by without any correction. Seems a bit much.

Can you provide more insight on this ratio and what its significance is?

There is some discussion of it here in this post: https://endmyopia.org/qa-high-astigmatism-low-myopia-sph-to-cyl-ratio-control/

Now that I re-read your post this is not relevant since I believe you were talking about your normalized. Do you have a set of differentials for close-up work?

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I was talking about normalized yes. For diffs I’ve been using +1.5 SPH (either reading glasses on top of contacts or I have both in regular glasses) though after ordering this prescription with the reduced cylinder I realized having an extra -0.25 SPH in my left eye might help for low light reading to bring the acuity to the same place. One of the weird bits is that I had strabismus as a child and surgery to correct it so I have no depth perception and my eyes seem to work together less than normal.

I played with ditching the astigmatism in my left eye but it required quite a bit of additional SPH and I was worried that might be suboptimal. Does CYL just directly translate to correction on one axis? i.e. -2.5 SPH plus -1.25 CYL means -3.75 effective SPH along the axis?

Yes that’s the idea.

Changes can be pretty profound in the first three months and I probably would have approached your situation differently, focusing exclusively on differentials. It is suggested that you are unlikely to notice removal of CYL of less than -1.00 from your differentials, unlike for distance. If you are getting decent vision with normalized at -0.75 CYL this might have been a good move to try in your diffs. But it also would have meant switching completely to glasses for a spell until any ciliary strain and over-correction are eliminated. Maybe something to consider if your current experiment is unsuccessful.

Don’t worry too much about poor lighting conditions. I keep an older pair of stronger lenses around to deal with that when necessary (driving, etc.) and others do too.

So let me see if I understand:

  1. Optimize for no CYL in diffs even if it means -0.75 additional SPH to replace the -1.25 CYL.
  2. Continue with present path of partial CYL reduction in normalized? Or would you recommend trying to see if I can tolerate higher SPH as a replacement there too?

I should check again because I was a little wary of increasing SPH by so much in my diffs but perhaps I should revisit it with the lens test kit to see what’s tolerable. I recall that text got some blur but that dialing up the SPH in the diffs did ameliorate some of that.

See Step 3 in this post on reducing prescription complexity: https://endmyopia.org/pro-topic-how-to-reduce-prescription-complexity/

I understand this to mean that your diffs should have a bifocal reduction (-1.50 is the most common) and also eliminate CYL, since it’s so low. You may have to play with it a bit to dial in what’s best for your eyes. Ideally you want a little bit of blur challenge in close-up at an ergonomically comfortable distance.

I would not mess with normalized so soon, but wait at least a few weeks/months for any over-correction and ciliary spasm to be released. You may find that one eye changes more rapidly than the other so it’s important to do your cm measurements to see what’s happening in real time. You may also find that your eyes adapt to your diffs very quickly, as evidenced by having to move further and further away from your screen to achieve any blur challenge.

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Despite concerted efforts I didn’t find a stark improvement that I would expect from correcting ciliary spasm even with reading glasses/diffs full time for close work. It seems possible that I didn’t have a lot of ciliary spasm at present.

However, after running through a 90 day supply of contacts at reduced
L: -2.5 SPH -0.75 CYL
R: -3.75

I seem to be back to 20/20! Ordered new contacts at +0.25. Once I hit 20/20 on those I will safely conclude that endmyopia isn’t bullshit :wink:

One note is that glasses seemed to require an additional -0.25-0.5 relative to contacts, and I still get better clarity with contacts most of the time. After playing around with the lens test kit, I’m going to stick with:
L: -2.5 SPH -0.75 CYL
R: -4.0

Whereas the new contacts:
L: -2.25 SPH -0.75 CYL
R: -3.5 SPH

Contacts aren’t available with less CYL so I think I’ll do a notch or two of SPH reduction before trying to eliminate the CYL though I did order -3 SPH contacts just in case those work. Though on second thought those might be too strong XD

For those wandering by, most of the time I wear reduced normalized contacts and carry a pair of +1.5 or +1.75 reading glasses. I’ve also ordered a pair of -0.25 glasses in case I need driving. I also ordered regular normalized and diff glasses as specified which I try to use 1 day a week in lieu of contacts.

Do you still feel that CYL correction is absolutely necessary for distance? Have you tried eliminating CYL and bumping up SPH to compensate with your test lens kit?

If you haven’t noticed, I detest that small amount of CYL you have.

It is your username after all :wink:

I was pretty jacked up on CYL for about 2 full years and when I tried to axe the full 1.25 it was too much to do all in one go and I wasn’t able to read comfortably clear text (the eye with the cyl is my dominant one which was a bit disorientating). I was going to see if I could use the -3.0 SPH contacts instead of the -2.25 -0.75 i the L since I seem to have better luck with less correction in contacts producing acceptable clarity. I think the contacts ETA is Saturday so I’ll report back then.

They really snuck the CYL in there didn’t they. I had the whole normal progression:
0.75 => 1.5 => 2.0 => split the power and give less to my dominant eye => keep going up and slowly add in cylinder.

It’s annoying…

Misspelling and all :smile:

Most excellent. If that works then you automatically get it out of your close-up, since you wear readers over contacts. That is where you potentially get the most benefit - CYL in your diffs pretty much guarantees it being necessary for distance.

Fingers crossed for you.

Nick – how did it work out?

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I think I’m going to continue with the straight 0.25 reduction in the dailies without the astigmatism change for now.

The Air Optix (especially the astigmatism ones) don’t fit my eyes as well — perhaps they’ve been abused into the shape of Dailies contacts (which are also a tad thinner).

The -3 diopter contacts didn’t seem to work very well either — in the left may be a little much given that my current astigmatism contacts are -2.25 SPH and -.75 CYL so I’ll save the last few for when my right eye improves (at -3.5 at the moment).

The dailies with the 0.25 reduction was a quite noticeable transition in acuity. My sense is that there has been improvement since I started wearing the lowered prescription though. The fit juggling around on my eyeball seems to substantially effect acuity more than the blur associated with undercorrection.

I realized that my axis measurement was off in the glasses (surprisingly my eyes have matched the axis to the 160 contacts I wore for a year which was a change relative to the 150 glasses axis from two years ago). I think I may experiment with reduced astigmatism correction in my glasses to -.5 for the next step since the jump from 0.75 to 0 seems a little aggressive at the moment since it’s in the dominant eye (not to mention I probably have some residual that hasn’t fixed from the 1.25 I started at).

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I wore toric lenses with a -2 sph and -1 cyl when I started EM. I quit the contacts completely because the toric lense got uncomfortable. I don’t know if this was the best thing to do but I completely dropped the CYL because it bothered me. First the with close work astigmatism was not noticeable and the CLY correction I had seemed to be too much. I found it too complicated to try to get it right. My astigmatism in each eye goes it different directions. Second I didn’t like the CYL correction in my glasses. Although it cleared up some of the blur, when I would turn my head it was almost like I could see the correction in the lenses. The sign would get longer or shorter depending on the angle I looked at it, and when I wore toric lenses if I blinked and didn’t get them to line up just right it would cause blurring. It has been 2 years now and I am down to -.50 sph normalized. I still have some astigmatism (about -.50) but it doesn’t bother me. I do notice it the father away the object is. I see good without glasses most of the time. If my eyes get tired I just wear my glasses. If I am driving at night I use a higher sph correction. Dropping CYL completely worked for me it just made everything easier. My astigmatism is gradually fading. I am not sure if having CYL in my lenses would have helped me improve faster or not I could never get it to feel right when I had it in. Dropping it completely worked for me but it may not be the best hing for everyone though.


Alright! After going through most of the aforementioned straight SPH reduction, I tried again with the contact combination:
L: -3 SPH
R: -3.5 SPH

And it wasn’t the most amazing but I decided to just grin and bear it and didn’t get any horrifying headaches. So I’m officially off of astigmatism. I ordered glasses at:
L: -3.25
R: -3.75
And after switching to those I think I’m on the right track. After a week, acuity is much better in the right than the left (not sure if this means the right eye is adjusting faster since it was closer to optimal and didn’t experience the CYL shock) but I think I’ll make the next reduction:
L: -3.25
R: -3.50
to try and get them closer and give my left eye a little extra time. Hopefully I will be able to get my left eye back to reasonable acuity without adding any CYL in the glasses. Guess time will tell :slight_smile:


Is that right eye move to -3.75 trading cylinder for sphere?

No the left eye had been at -2.25 SPH -0.75 CYL with contacts. In order to get it in striking distance with acuity I had to increase to -3.0 with contacts. My previous glasses prescription (since it requires a bit more than contacts) was:
Right -4.00
Left -2.75 SPH / -0.75 CYL
And I now have:
R: -3.75
L: -3.25